This filter recognizes as valid characters all digits, plus left and
right parentheses, minus sign, plus sign, x (for extension), the space
character, the number sign, the asterisk, question mark and period,
uppercase letters (for the following map).

convert

public char convert(char character,
int status)

Passes character through phone text filter.

The current behaviour of this filter is to automatically ALT the characters
so that numbers, the period, and the dash are entered by default. When SHIFT is pressed,
uppercase letters are returned. Holding ALT allows for 'x' to be entered (in case there is an
allowable symbol on this key).